Horizontal rectus muscle transplantation for recurrent and residual strabismus.

Purpose: To report outcomes of muscle transplantation for recurrent/residual strabismus. Retrospective, multicentric, observational study.  Methods: We retrospectively reviewed records of all patients operated at three institutes who underwent transplantation of the resected muscle for re-operations for residual/recurrent strabismus from January 1, 2018, to December 31, 2019. Data were collected regarding age, gender, visual acuity, type of strabismus, fixation preference, associated amblyopia, the surgical procedure performed, preoperative and postoperative primary position deviation, limitation of ductions, associated intra-operative and post-operative complications. Surgical success was defined as heterotropia less than or equal to 8 PD, and cosmetic success was defined as manifest deviation ≤12 PD (at 6 weeks follow up). Results: During this period, we identified records of seven patients (5 men: 2 women, median age: 24 years) who underwent muscle transplantation for residual/recurrent strabismus. Six patients underwent extraocular muscle surgery for residual/recurrent exotropia (XT) and one for residual esotropia (ET). In all the patients, median pre-operative primary position deviation reduced from 40 prism diopters (PD) (range: 30 to 55 PD) to 8 PD (range: 6 PD ET to 10 PD XT) at six-weeks follow-up. Four patients had residual exotropia (10-16PD), two had orthotropia and one patient had small-angle esotropia (6PD) at the last follow-up. Excluding two patients who underwent supramaximal re-recession of lateral rectus (≥11 mm from insertion) and re-resection of medial rectus, 3/5 (60%) patients achieved surgical success, and all (100%) achieved cosmetic success at six-weeks-follow-up. There was mild (up to -1) limitation of duction in all patients except one patient (-2 limitation of abduction) who underwent re-recession of lateral rectus to 11 mm from insertion along with medial rectus re-resection and muscle transplant procedure. No intra-operative or post-operative complications were encountered. No patient reported postoperative diplopia. Conclusions: This study describes the feasibility and successful use of muscle transplantation procedure to correct residual/recurrent strabismus, with or without re-recession, especially in patients planned for surgery in one eye. However, larger prospective studies with longer follow-ups will be needed to establish long-term outcomes and correction achieved from this procedure, and comparison with other approaches for reoperations.